Is matter around us pure Worksheet-3

Is matter around us pure Worksheet-3

11. The cause of Brownian movement is :

A. heat changes in liquid state

B. convection currents

C. impact of molecules of dispersion medium on on dispersed phase

D. attractive forces between the particles of dispersed phase and dispersion medium.

12. A mixture of ammonium chloride and sodium chloride can be separated by :

A. crystallisation                           B. hand pricking

C. by sublimation                         D. centrifugation

13. Which of the following is not a chemical change?

A. rusting of iron                          B. cooking of food

C. freezing of water                      D. digestion of food.

14. Which of the following will show Tyndall effect?

A. starch solution                         B. sodium chloride solution

C. copper sulphate solution       D. sugar solution.

15.  Size of particles in a colloidal solution ranges from :

A. 10^–5 cm to 10³ cm                    B. 10^–5 cm to 10^–7 cm

C. 10^–2 cm to 10^–4 cm                  D. None is correct.

16. An emulsion is a colloidal solution formed by mixing:

A. two miscible liquids                B. any two liquids

C. any two gases                           D. two immiscible liquids

17. Colloidal particles can be normally seen by :

A. naked eye                                  B. ordinary microscope

C. electron microscope               D. telescope.

18. A pure substance can be :

A. an element only

B. a compound only

C. either element or compound

D. any substance.

19. At room temperature, a non-metal which is a liquid is:

A. sulphur         B. bromine        C. chlorine         D. nitrogen

20. In which of the following, dispersed phase is a liquid and dispersion medium is a gas?

A. cloud                                          B. smoke

C. gel                                               D. soap bubble

Answer Key:

11. C

Explanation: Zig-zag path of colloidal particles is called Brownian Movement. Zig-zag path of particles is due to collision of particles of dispersed phase and dispersion medium.

12. C

Explanation: Ammonium chloride sublimes where as sodium chloride melts on heating. A mixture of ammonium chloride and sodium chloride can be separated by sublimation.

13. C

Explanation: Freezing of water is a physical change. On freezing only state of water changes its chemical composition remains the same.

14. A

Explanation: Starch solution because it is a colloidal solution.

15. B

Explanation: It is between 10^–5 cm to 10^–7 cm to 10^–7 cm (10^–9 m)

16. D

Explanation: Emulsion is a mixture of two immiscible liquids. Milk, Cod liver oil, tonics in liquid form etc. are emulsions.

17. B

Explanation: Ordinary microscope is used to view colloidal particles.

18. C

Explanation: It can be either an element or a compound.

19. B

Explanation: Bromine is liquid at room temperature.

20. A

Explanation: In cloud, water drops are suspended in air.